Malignant pleural mesothelioma masquerading as a chest wall soft tissue tumor

Abstract Malignant pleural mesothelioma (MPM) typically presents as diffuse pleural thickening accompanied by pleural effusion, whereas cases presenting primarily with a localized chest wall mass are extremely rare and highly deceptive in clinical practice. We herein report the case of a 67-year-old male patient without a definitive history of asbestos exposure, who presented with a right anterior chest wall mass and chest pain. The preoperative needle biopsy merely indicated a poorly differentiated malignant tumor. After undergoing extended resection of the right anterior chest wall malignancy, the patient was definitively diagnosed with biphasic malignant pleural mesothelioma (T4N0M0 IIIB) through detailed pathological and immunohistochemical examinations, and experienced tumor recurrence only two months postoperatively. This case highlights the significant challenges in the preoperative diagnosis of atypical MPM, indicating that when confronting atypical pleural tumors in clinical practice, it is imperative to rely on adequate needle biopsy, extensive immunohistochemistry, and even multidisciplinary team (MDT) discussion to determine the pathological origin. This approach is crucial to avoid therapeutic decision-making errors caused by misdiagnosis and to formulate the most appropriate comprehensive treatment strategy for the patient.